Ventilating device

ABSTRACT

A ventilating device includes a housing; a gas concentration detector; a passage portion defining an outside air passage and an inside air passage; a permeable membrane disposed at an interface between the outside air passage and the inside air passage; an air sending portion to generate at least one of a flow of outside air in the outside air passage and a flow of inside air in the inside air passage; and a controller. The controller controls at least one of the flow of inside air and the flow of outside air by controlling the air sending portion, based on a gas concentration of a predetermined gas detected by the gas concentration detector.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2010-149675 filed on Jun. 30, 2010, and Japanese Patent Application No. 2011-48931 filed on Mar. 7, 2011, the disclosures of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a ventilating device.

2. Description of Related Art

Conventionally, a ventilating device to control gas concentration in a temperature-regulated chamber is known. For example, fruits and vegetables are kept fresh by controlling oxygen concentration and carbon dioxide concentration in a refrigerator or a freezer to store the fruits and vegetables based on a Modified Atmosphere (MA) method or a Controlled Atmosphere (CA) method.

The MA method has a direct method disclosed by JP-A-2008-50027 and an indirect method disclosed by JP-A-6-11235, for example. In the direct method, outside air is supplied directly into a chamber for ventilation. In the indirect method, oxygen and carbon dioxide are supplied into a chamber through a packing material with a predetermined permeation velocity. The indirect method is called as MA packaging.

The CA method is disclosed by JP-A-3-82587, for example. Oxygen concentration and carbon dioxide concentration in a chamber are controlled using adsorption separation or membrane separation. The CA method is called as CA storage.

However, in the direct method, because all gasses including nitrogen in the chamber are changed, a temperature in the chamber fluctuates widely, so that thermal load necessary for readjusting the temperature of the chamber is increased.

In the indirect method, a permeation velocity of gas depends on a kind of the packing material. Because an optimum oxygen concentration and an optimum carbon dioxide concentration depend on a kind of the fruits and vegetables, the kind of the packing material should be changed, depending on the kind of the fruits and vegetables.

In the CA storage, a pressurizing pump and a depressurizing pump are necessary for obtaining a predetermined gas concentration, so that a system of the CA storage becomes complicated. Further, a running cost of the CA storage becomes high.

SUMMARY OF THE INVENTION

In view of the foregoing and other problems, it is an object of the present invention to provide a ventilating device.

According to an example of the present invention, a ventilating device includes a housing, a gas concentration detector, a passage portion, a permeable membrane, an air-sending portion and a controller. A temperature of inside air of the housing is to be controlled. The gas concentration detector detects a concentration of a predetermined gas in the housing. The passage portion defines an outside air passage through which outside air of the housing flows, and an inside air passage through which inside air of the housing flows. The permeable membrane is disposed at an interface defined between the outside air passage and the inside air passage in a manner that a first face of the permeable membrane contacts the outside air flowing through the outside air passage and that a second face of the permeable membrane contacts the inside air flowing through the inside air passage. Gas permeates the permeable membrane selectively between the outside air passage and the inside air passage. The air-sending portion generates at least one of a flow of the outside air in the outside air passage and a flow of the inside air in the inside air passage. The controller controls the air sending portion.

The controller controls at least one of the flow of the outside air and the flow of the inside air by controlling the air sending portion based on the concentration of thepredetermined gas detected by the gas concentration detector.

Accordingly, the concentration of the predetermined gas can be easily and accurately controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a schematic diagram illustrating a ventilating device according to a first embodiment of the present invention;

FIG. 2 is a schematic sectional view illustrating a permeable membrane of the ventilating device;

FIG. 3 is a schematic diagram illustrating a ventilating device according to a second embodiment of the present invention;

FIG. 4 is a schematic sectional view illustrating a permeable membrane unit of a ventilating device according to a third embodiment of the present invention;

FIG. 5 is a schematic sectional view illustrating a permeable membrane unit of a ventilating device according to a third embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating a ventilating device according to a fourth embodiment of the present invention;

FIG. 7 is a schematic diagram illustrating a ventilating device according to a fifth embodiment of the present invention;

FIG. 8 is a schematic diagram illustrating a ventilating device according to a sixth embodiment of the present invention; and

FIG. 9 is a schematic diagram illustrating a ventilating device according to a seventh embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT First Embodiment

A first embodiment of the present invention will be described with reference to FIG. 1 and FIG. 2. As shown in FIG. 1, a ventilating device 1 has a housing 10 that accommodates an object inside. The housing 10 may correspond to a refrigerator, a freezer or a freezing container to store perishable green grocery such as fruit or vegetable. The housing 10 has an air-conditioner (not shown) for controlling inner air to have a predetermined temperature. The air-conditioner has a known refrigerating cycle used to cool air to be conditioned, and a known electrical or combustion type heater used to heat air to be conditioned.

An air-circulating blower 11, an O₂ sensor 12, a CO₂ sensor 13, and a humidity sensor 14 are arranged in the housing 10. The air-circulating blower 11 circulates the inside air entirely in the housing 10. The O₂ sensor 12 detects oxygen concentration in the inside air. The CO₂ sensor 13 detects carbon dioxide concentration in the inside air. The humidity sensor 14 detects humidity in the inside air.

Further, a permeable membrane unit 20 is arranged in the housing 10. The permeable membrane unit 20 has a passage portion 21 that defines an outside air passage 22 and an inside air passage 23. The passage portion 21 is arranged to straddle the housing 10 in a manner that the inside air passage 23 is defined inside of the housing 10 and that the outside air passage 22 is defined outside of the housing 10.

A permeable membrane 24 is disposed at an interface defined between the outside air passage 22 and the inside air passage 23. A part of wall face of the housing 10 is defined by the permeable membrane 24. In the outside air passage 22, outside air of the housing 10 flows along a surface of the permeable membrane 24. In the inside air passage 23, inside air of the housing 10 flows along a surface of the permeable membrane 24.

The permeable membrane 24 has characteristics described below. If a certain type of gas such as oxygen, carbon dioxide, or water vapor has a concentration difference between the inside air and the outside air, the gas permeates the membrane 24 easily. If the other gas such as nitrogen that does not have the concentration difference, the other gas hardly permeates the membrane 24.

The permeable membrane 24 may be a gas permeable film made of polymer such as silicone, a porous member made of cellophane or ceramic, a non-woven cloth, or the like. Outside air contacts a surface of the permeable membrane 24 exposed to the outside air passage 22, and inside air contacts a surface of the permeable membrane 24 exposed to the inside air passage 23, so that the gas having the concentration difference selectively permeates the permeable membrane 24.

A permeability of the permeable membrane 24 is achieved by the concentration difference of the gas between inside air and outside air. The permeability of the permeable membrane 24 is achieved without a huge pressure difference generated by a pressure difference generating device such as a vacuum pump. That is, the permeability of the permeable membrane 24 is achieved even when inside air and outside air have no pressure difference.

Surface area per volume of the permeable membrane 24 is made large by folding and pleating a membrane into a board shape, or by layering flat membranes. Thereby, the permeability of the permeable membrane 24 is improved.

Further, support members (not shown) are layered in the permeable membrane 24. The support member is made of ceramic, fiber, porous metal, porous resin, or resin screen mesh, for example. Although a thickness of the permeable membrane 24 is small enough for gas permeation, the support members support and strengthen the membrane 24.

The permeable membrane 24 has pores on the surface or/and inside. A diameter of the pore is equal to or smaller than a mean free path of gas to permeate the membrane 24 such as O₂, CO₂ or H₂O. The mean free path represents a distance that a gas molecule moves from when the gas molecule collides with other gas molecule to when the gas molecule collides with another gas molecule. The mean free path depends on a type of the gas molecule.

Thereby, when gas permeates the permeable membrane 24, Knudsen flow becomes dominative in a flow of the gas permeating the membrane 24. “Knudsen flow” represents a lean gas flow, so that molecule movement in the lean gas flow becomes a matter to be discussed. “Knudsen flow” is characterized in that a gas permeation speed depends on a molecular weight of the gas. “Knudsen flow becomes dominative” represents that the gas permeation speed becomes dependant on the molecular weight of the gas.

The flow of gas permeating the membrane 24 is changed in order of viscous flow, Knudsen flow, and dissolution diffusion flow, as the pore diameter of the membrane 24 is made smaller. A lower limit of the pore diameter that causes Knudsen flow is about 1 nm that corresponds to a molecule size. An upper limit of the pore diameter that causes Knudsen flow is about 50 nm that is equal to or less than the mean free path of gas.

In viscous flow, because gas flows from a high pressure point to a low pressure point, a direction of the gas flow is determined by a pressure difference between inside air and outside air, that corresponds to a difference in a total pressure. Therefore, gas not having the concentration difference between inside air and outside air such as N₂ permeates the permeable membrane 24 based on the pressure difference between inside air and outside air. That is, selective permeation cannot be performed between gas having concentration difference and gas not having concentration difference. The concentration difference between inside air and outside air may correspond to a difference in a partial pressure.

In Knudsen flow, a molecule collides with a wall face of a pore in the membrane 24 before the molecule collides to other molecule. Therefore, selective permeation of gas having concentration difference can be performed without being affected by a pressure difference between inside air and outside air. The selective permeation of gas having concentration difference can be performed by making the pore diameter of the permeable membrane 24 equal to or less than the mean free path of gas to permeate the membrane such as O₂, CO₂ or H₂O.

In dissolution diffusion flow, gas molecule dissolves in a surface of the permeable membrane 24 located upstream in gas flow, and moves inside of the permeable membrane 24 by molecular diffusion. Therefore, gas permeation is not affected by a pressure difference between inside air and outside air. However, a velocity of gas permeating the membrane 24 is made slower, as the pore diameter of the membrane 24 is made smaller. Therefore, the pore diameter of the permeable membrane 24 is required to be made larger so as to secure a predetermined gas permeation speed. For example, the pore diameter of the permeable membrane 24 may be at least more than 1 nm, which is the molecule size.

An outside air-sending portion 25 generates a flow of outside air, and is arranged in the outside air passage 22. An inside air-sending portion 26 generates a flow of inside air, and is arranged in the inside air passage 23. The air-sending portion 25, 26 is a fluid machinery that gives kinetic energy to gas or that raises gas pressure with a gas compression ratio less than 2. For example, the air-sending portion 25, 26 may be a fan, a blower, or the like. The air-sending portion 25, 26 has a ventilating fan and a motor to drive the ventilating fan to rotate.

As shown in FIG. 1, outside air in the outside air passage 22 flows from left to right, and inside air in the inside air passage 23 flows from right to left. The air-circulating blower 11 generates a flow of inside air circulating in the housing 10. However, in a case where the inside air-sending portion 26 is not operated, the flow of inside air is not generated in the inside air passage 23.

When the air-sending portion 25, 26 is not operated, gas stays without moving around a surface of the permeable membrane 24. In that case, a difference in the gas concentration between inside air and outside air becomes small, so that the gas permeation is less performed. If at least one of the air-sending portions 25, 26 is operated, the gas is restricted from staying, so that the gas permeation is advanced.

The ventilating device 1 has a controller 50. The controller 50 has a well-known microcomputer having CPU, ROM, RAM, and the like, and a peripheral circuit. The controller 50 conducts various calculations and processing based on a control program memorized in the ROM, and controls various devices connected to an output side of the controller 50. Sensor signals of the O₂ sensor 12, the CO₂ sensor 13, and the humidity sensor 14 are input into the controller 50. The controller 50 outputs a control signal to the air-sending portion 25, 26, so as to perform a ventilating control.

Fruit or vegetable breathes while stored in the housing 10. Therefore, compared with atmosphere, oxygen concentration is low and carbon dioxide concentration is high, in the housing 10. It is known that the breathing of fruit or vegetable is reduced where the oxygen concentration is low and where the carbon dioxide concentration is high, so as to keep the freshness for a long time. In contrast, if the oxygen concentration becomes low excessively, fruit or vegetable may perish with metabolic disorder. In this case, a strange taste, a strange smell, and rotting may occur.

Fruit or vegetable contains much water, so that a relative humidity in the housing 10 often becomes high, due to water emitted from the fruit or vegetable stored in the housing 10. Dew condensation may occur in the housing 10, if the relative humidity becomes too high. Fruit or vegetable will wither in the housing 10, if the relative humidity becomes too low. The both cases are not desirable to keep the freshness of the fruits and vegetables. Thereby, it is necessary to control the oxygen concentration, the carbon dioxide concentration, and the humidity in the housing 10, within a predetermined range to be suitable to store the fruits and vegetables.

Optimal oxygen concentration, optimal carbon dioxide concentration, and optimal humidity of fruits and vegetables are different based on kinds of the fruits and vegetables. For example, as for a banana, it is desirable to be stored where the oxygen concentration is 2-5%, where the carbon dioxide concentration is 2-5%, and where the relative humidity is 90-95%. As for a strawberry, it is desirable to be stored where the oxygen concentration is 5-10%, where the carbon dioxide concentration is 15-20%, and where the relative humidity is 90-95%. As for a mango, it is desirable to be stored where the oxygen concentration is 3-5%, where the carbon dioxide concentration is 5-10%, and where the relative humidity is 85-90%. In the present embodiment, the controller 50 controls the oxygen concentration, the carbon dioxide concentration, and relative humidity by controlling the air-sending portion 25, 26, based on signals output from the O₂ sensor 12, the CO₂ sensor 13 and the humidity sensor 14.

The ventilation control of the air-sending portion 25, 26 performed by the controller 50 will be described. The ventilation control is performed based on a control program memorized in the ROM of the controller 50, for example.

The ventilation control is described using a banana as a storage subject, for example. However, if a kind of the fruits and vegetables is changed, the ventilation control will also be changed. In the case of using the membrane, each of the oxygen concentration and the carbon dioxide concentration is changed with satisfying a condition that a sum of the oxygen concentration and the carbon dioxide concentration is approximately equal to 21%.

[oxygen concentration+carbon dioxide concentration≈21%]

For example, when the oxygen concentration is 15%, the carbon dioxide concentration is 6%. Moreover, if the oxygen concentration becomes equal to or lower than 1% or if the carbon dioxide concentration becomes equal to or higher than 7%, the banana will deteriorate (referring to “1. controlled Atmosphere” in “GUIDE to FOOD TRANSPORT”, published by Mercantila Publishers).

The ventilation control is performed mainly based on one of the oxygen concentration and the carbon dioxide concentration, considering a balance between a recommended concentration range to keep the banana fresh and an injurious concentration range of the banana. In the case of banana, the ventilation control is performed based on the carbon dioxide concentration, as a main. In other words, the carbon dioxide concentration has a priority to the oxygen concentration in the ventilation control for banana. In this embodiment, the carbon dioxide is controlled to have a concentration in range of 2-5%, and the oxygen is controlled to have a concentration in range of 16-19%.

An example of the ventilation control using the air-sending portion 25, 26 is described in the case where the banana is stored in the ventilating device 1.

It is determined whether the carbon dioxide concentration detected by the CO₂ sensor 13 reaches an upper limit (5%) of the concentration range. If the carbon dioxide concentration exceeds the upper limit, the air-sending portions 25, 26 are activated, so that outside air and inside air are supplied, respectively, to the both sides of the permeable membrane 24. A ventilation volume of the air-sending portion 25, 26 is controlled by adjusting fan rotation output, based on the carbon dioxide concentration detected by the CO₂ sensor 13. The adjustment is performed by, for example, ON-OFF control or PID control.

Thus, carbon dioxide gas moves through the permeable membrane 24 from inside to outside, so that the carbon dioxide concentration in the housing 10 is lowered. At the same time, a concentration difference of other gas such as CO₂ and H₂O becomes small between inside air and outside air, by operating the air-sending portions 25, 26.

After the air-sending portions 25, 26 are activated, it is determined whether the carbon dioxide concentration reaches a lower limit (2%) of the concentration range. If the carbon dioxide concentration reaches the lower limit, at least one of the air-sending portions 25, 26 is stopped. Thereby, gas movement between outside air and inside air through the permeable membrane 24 is stopped, so that the lowering of the carbon dioxide concentration stops in the housing 10. Thereafter, if the carbon dioxide concentration in the housing 10 is raised again by breathing of banana, above mentioned process is repeated.

When the carbon dioxide concentration is in the predetermined range (2-5%) and when the oxygen concentration is in the predetermined range (16-19%), it is determined whether the humidity detected by the humidity sensor 14 exceeds the upper limit (95%) of the recommended range. If the humidity exceeds the upper limit, the air-sending portions 25, 26 are activated, so as to supply outside air and inside air, respectively, to the both sides of the permeable membrane 24. The ventilation volume of the air-sending portion 25, 26 is controlled based on the humidity detected by the humidity sensor 14. Specifically, as a difference between the humidity detected by the humidity sensor 14 and the upper limit is larger, the ventilation volume of the air-sending portion 25, 26 is increased, so as to raise molecule exchange efficiency in the permeable membrane 24.

Therefore, water vapor moves through the permeable membrane 24 from inside to outside, so that the humidity is lowered in the housing 10. At the same time, a concentration difference of other gas such as O₂ and CO₂ becomes small between inside air and outside air, by operating the air-sending portions 25, 26.

If the outside humidity is higher than the inside humidity, the humidity cannot be lowered in the housing 10, even if the air-sending portions 25, 26 are activated. In a case where a humidity sensor to detect outside humidity is arranged, if the inside humidity exceeds the upper limit, and if the outside humidity is lower than the inside humidity, the air-sending portions 25, 26 may be activated.

After the air-sending portions 25, 26 are activated, it is determined whether the humidity reaches the lower limit (90%). If the humidity reaches the lower limit, the air-sending portions 25, 26 are stopped, and the gas movement between inside air and outside air thorough the permeable membrane 24 is stopped. Thus, the lowering in the humidity in the housing 10 is stopped. Thereafter, if the humidity in the housing 10 is raised again by breathing of banana, above mentioned process is repeated.

While the air-sending portions 25, 26 are activated, a flow rate of outside flow and a flow rate of inside flow are made different from each other, thereby promoting the gas permeation through the permeable membrane 24.

FIG. 2 is a schematic view illustrating an outside air flow in the outside air passage 22 and an inside air flow in the inside air passage 23. A flow rate Q2 of inside air in the inside air passage 23 is larger than a flow rate Q1 of outside air in the outside air passage 22. Further, a static pressure P2 in the inside air passage 23 is higher than a static pressure P1 in the outside air passage 22.

In the case where the flow rate Q1 of outside air differs from the flow rate Q2 of inside rate, and in the case where the static pressure P1 differs from the static pressure P2, as shown in dashed lines of FIG. 2, a flow can be generated in a direction approximately perpendicular to the surface of the permeable membrane 24. Therefore, the staying of gas near the surface of the permeable membrane 24 is reduced or eliminated. Thus, the molecule exchange efficiency of the permeable membrane 24 is raised, and the gas permeation is promoted.

According to the present embodiment, due to the permeable membrane 24, only the gas having the concentration difference between inside air and outside air such as O₂, CO₂, and H₂O can be moved. In contrast, the gas not having the concentration difference between outside air and inside air such as N₂ does not move between inside air and outside air. Therefore, conditioned, specifically cooled, inside air can be prevented from being emitted to outside air unnecessarily. Accordingly, a thermal load of the ventilating device 1 can be decreased.

Further, the oxygen concentration, the carbon dioxide concentration, and the humidity can be suitably controlled by controlling the air-sending amount of the air-sending portion 25, 26 based on the sensor signals output from the O₂ sensor 12, the CO₂ sensor 13, and the humidity sensor 14. Even if a type of the fruits and vegetables stored in the housing 10 is changed, the oxygen concentration, the carbon dioxide concentration, and the humidity can be suitably kept within the predetermined range.

Due to the concentration difference between inside air and outside air, gas can pass through the permeable membrane 24. Therefore, the gas concentration in the housing 10 can be controlled by a simple structure that only generating the flows of inside air and outside air with the air-sending portion 25, 26.

Second Embodiment

A second embodiment of the present invention will be described with reference to FIG. 3. In each of the following embodiments, the components, which are similar to those of the first embodiment, will not be described again for the sake of simplicity. Only the differences from the first embodiment will be described below.

As shown in FIG. 3, in the second embodiment, the inside air-sending portion 26 of the first embodiment is not arranged in an inside air passage 23, and an inside passage switching door 27 is arranged adjacent to an inlet of the inside air passage 23. An inside air flow generated by an air-circulating blower 11 circulates in a counterclockwise direction. Thereby, a right side of FIG. 3 becomes an inlet of the inside air passage 23 and a left side of FIG. 3 becomes an outlet of the inside air passage 23. The inside, air passage 23 is located in an upper part of the housing 10.

The inside passage switching door 27 switches the inside air passage 23, and is rotated by a motor. If the switching door 27 closes the inside air passage 23 as shown by a dashed line in FIG. 3, the inside air flow generated by the air-circulating blower 11 is not introduced to the inside air passage 23.

In contrast, if the switching door 27 opens the inside air passage 23 as shown by a continuous line in FIG. 3, the inside air flow is let to the inside air passage 23. Further, by controlling an opening degree of the switching door 27, a flow rate introduced to the inside air passage 23 is controlled.

That is, when the opening degree of the switching door 27 is made large, the flow rate of inside air in the inside air passage 23 becomes large. Further, when the opening degree of the switching door 27 is made small, the flow rate of inside air in the inside air passage 23 becomes small.

The inside passage switching door 27 is controlled by a control signal output from a controller 50. That is, in the second embodiment, based on sensor signals output from an O₂ sensor 12, a CO₂ sensor 13, and a humidity sensor 14, the controller 50 controls an outside air-sending portion 25 and the switching door 27.

According to the second embodiment, by using the inside air flow generated by the air-circulating blower 11, an inside air-sending portion 26 having a motor may be unnecessary. Thus, a configuration of a ventilating device 1 may be simplified.

Third Embodiment

A third embodiment of the present invention will be described with reference to FIG. 4 and FIG. 5.

FIG. 4 corresponds to another variation of the first embodiment having the inside air-sending portion 26. In an example of FIG. 4, an inside air-sending portion 26 has a fan 26 a, a motor 26 b, and a drive gear 26 c. The motor 26 b controls a rotation of the fan 26 a. The drive gear 26 c is fixed to an end of a drive shaft of the motor 26 b.

An outside air-sending portion 28 has a fan 28 a and a driven gear 28 b. The outside air-sending portion 28 of the third embodiment does not have a motor. The outside air-sending portion 28 is configured as a fan driven passively by the inside air-sending portion 26.

A power transmitter 29 transmits a rotation drive force of the fan 26 b of the inside air-sending portion 26 to the outside air-sending portion 28. The power transmitter 29 has a drive shaft 29 a, and inside and outside gears 29 b, 29 c that are arranged in both ends of the shaft 29 a, respectively. The drive shaft 29 a of the power transmitter 29 is arranged to overlap an outside air passage 22 and an inside air passage 23.

The inside gear 29 b is fixed to the end of the drive shaft 29 a and is located in the inside air passage 23. The inside gear 29 b is engaged with the drive gear 26 c of the inside air-sending portion 26.

The outside gear 29 c is fixed to the end of the drive shaft 29 a and is located in the outside air passage 22. The outside gear 29 c is engaged with the driven gear 28 b of the outside air-sending portion 28.

As described above, when the inside air-sending portion 26 is activated, the motor 26 b drives the fan 26 a to rotate, and simultaneously drives the outside air-sending portion 28 to rotate. Thereby, when an inside air flow is generated in the inside air passage 23, an outside air flow is generated in the outside air passage 22 at the same time.

FIG. 5 corresponds to another variation of the second embodiment not having the inside air-sending portion 26. An example shown in FIG. 5 is different from an example shown in FIG. 4 in a configuration of the power transmitter 29. The power transmitter 29 in FIG. 5 has a fan 29 d to be driven to rotate by an inside air flow. The fan 29 d is arranged in an end of a rotation shaft 29 a on the side of the inside air passage 23.

That is, according to the example shown in FIG. 5, fluid energy of the inside air flowing in the inside air passage 23 drives the power transmitter 29 to rotate, and drives the outside air-sending portion 28 to rotate. Thereby, when an inside air flow is generated in the inside air passage 23, an outside air flow is generated in the outside air passage 22.

According to the third embodiment, an outside air-sending portion having a motor may be unnecessary. Thus, a configuration of the air-sending portion may be simplified.

Further, in a configuration shown in FIG. 4, a device arranged in the outside air passage 22 and a device arranged in the inside air channel 23 can be exchanged with each other. That is, when an outside air-sending portion 25 having a motor is arranged in the outside air passage 22, an inside air-sending portion 26 not having a motor is arranged in the inside air passage 23. Thereby, a rotation drive force of the outside air-sending portion 25 is transmitted to the inside air-sending portion 26 through the power transmitter 29.

Fourth Embodiment

A fourth embodiment of the present invention will be described with reference to FIG. 6.

As shown in FIG. 6, a ventilating device 1 has a condenser 30 and an evaporator 31 which define a refrigerating cycle. The condenser 30 is arranged in an outside air introducing passage 32 to which outside air is introduced. The evaporator 31 is arranged in an inside air circulation passage 33 through which inside air passes.

Temperature of outside air flowing in the outside air introducing passage 32 is raised by exchanging heat with a high temperature refrigerant in the condenser 30. Temperature of inside air flowing in the inside passage 33 is lowered by exchanging heat with a low temperature refrigerant in the evaporator 31.

The outside air introducing passage 32 is arranged in a lower corner of a housing 10. Other components of the refrigerating cycle such as compressor (not shown) are arranged under the condenser 30 in the outside air introducing passage 32. As shown in FIG. 6, the condenser 30 is arranged to extend approximately horizontally to the evaporator 31 near a right side wall of the housing 10. The evaporator 31 is slightly inclined toward the right side wall. In addition, the evaporator 31 is arranged upper than the condenser 30.

A fan of the condenser 30 sending outside air to the condenser 30 corresponds to an outside air-sending portion 25. A fan of the evaporator 31 sending inside air to the evaporator 31 corresponds to an inside air-sending portion 26.

The outside air-sending portion 25 is located downstream from the condenser 30 in an air flow. Outside air is supplied to the condenser 30 by being sucked by the air-sending portion 25.

The inside air-sending portion 26 is located upstream from the evaporator 31 in an air flow. Inside air blown by the inside air-sending portion 26 is supplied to the evaporator 31.

The ventilating device 1 is arranged as a freezing container, so that the inside air is usually cooled by passing through the evaporator 31.

A partition 34 is arranged in the housing 10 so as to divide the freezing container into inside area and outside area. In the inside area, inside air is circulated. In the outside area, outside air is introduced. A permeable membrane 24 is arranged in the partition 34. The permeable membrane 24 is located downstream from the condenser 30 in the outside air introducing passage 32, and is located downstream from the evaporator 31 in the inside air circulating passage 33. Outside air heated by the condenser 30 flows downward through the outside air introducing passage 32 from the condenser 30.

Further, a bypass passage 35 is arranged to lead outside air to an outside air passage 22 by bypassing the condenser 30. Due to the bypass passage 35, cooling efficiency of the ventilating device 1 can be maintained, even if a heat loss is increased when outside air heated by the condenser 30 contacts inside air cooled by the evaporator 31 via the membrane 24.

The outside air passage 22 and the bypass passage 35 are shown by dashed line in FIG. 6. The bypass passage 35 is located downstream from the condenser 30 in the outside air introducing passage 32. The bypass passage 35 and the outside air introducing passage 32 are arranged with each other in a depth direction of FIG. 6.

Outside air introduced through the bypass passage 35 flows to the permeable membrane 24 without passing through the condenser 30, so that the outside air is not affected by heat of the condenser 30. The bypass passage 35 is arranged to extend perpendicularly to the permeable membrane 24. Thus, outside air flowing in the bypass passage 35 is deflected perpendicularly at the membrane 24, and thereafter flows in the outside air passage 22.

In an inside air passage 23, an inside passage switching door 27 a, 27 b is arranged to connect the inside air passage 23 to the inside air circulation passage 33, or to disconnect the inside air passage 23 from the inside air circulation passage 33. The inside passage switching door 27 a is arranged upstream from the inside passage switching door 27 b in air flow.

In the same way as in the second embodiment, the inside passage switching door 27 a, 27 b is driven to rotate by a motor. The switching door 27 a, 27 b is controlled to be opened or closed by a controller 50 (not shown in FIG. 6), based on sensor signals output from an O₂ sensor 12, a CO₂ sensor 13, and a humidity sensor 14.

As shown in FIG. 6, outside air in the outside air passage 22 flows upward, and inside air in the inside air passage 23 flows downward. That is, in the present embodiment, inside air and outside air flow in counter state, so that a flow direction of the inside air is opposite to a flow direction of the outside air via the permeable membrane 24.

Inside air and outside air is defined to flow in cross state when inside air flows in a direction perpendicular to an outside air flow. Inside air and outside air is defined to flow in parallel state when inside air flows in a direction parallel to an outside air flow.

Molecule exchange efficiency becomes higher in order of the parallel state, the cross state, and the counter state. Thus, if inside air and outside air are set to flow in the counter state, molecule exchange can be effectively performed by the permeable membrane 24.

Further, heat exchange efficiency between inside air and outside air via the membrane 24, becomes higher in order of the parallel state, the cross state, and the counter state. Heat loss of the counter state is the highest. Therefore, if a balance between the molecule exchange efficiency and the heat loss is considered, inside air and outside air may be set to flow in the cross state.

According to the present embodiment, by using the condenser fan as the outside air-sending portion 25 and by using the evaporator fan as the inside air-sending portion 26, outside air and inside air are supplied to the permeable membrane 24 with existing devices. Therefore, a structure of the ventilating device 1 can be simplified.

Further, due to the bypass passage 35, outside air not affected by the condenser 30 can be supplied to the permeable membrane 24 located downstream from the condenser 30 in the outside air introducing passage 32. Therefore, temperature difference between outside air of the outside passage 22 and inside air of the inside passage 23 can be reduced, so that the heat loss may be reduced. Thus, loss in system efficiency may be reduced while inside air and outside air contact with each other via the membrane 24.

Fifth Embodiment

A fifth embodiment of the present invention will be described with reference to FIG. 7. In the fifth embodiment, compared with the forth embodiment, a position of a permeable membrane 24 is modified.

The permeable membrane 24 is arranged in a partition 34 separating an outside air introducing passage 32 and an inside air circulation passage 33. The permeable membrane 24 is located upstream from a condenser 30 in the outside air introducing passage 32, and is located downstream from an evaporator 31 in the inside air circulating passage 33.

A passage portion 36 defining an outside air passage 22 is arranged in the outside air introducing passage 32, and is located adjacent to the membrane 24. Outside air introduced to the outside air introducing passage 32 flows into an outside air passage 22 along the passage portion 36. Thus, outside air introduced to the outside air introducing passage 32 does not directly collide with the membrane 24.

The passage portion 36 extends Up to downstream side of the condenser 30 in the outside air introducing passage 32. Therefore, outside air passing through the outside air passage 22 flows downward from the condenser 30 without flowing through the condenser 30.

According to the present embodiment, by using a condenser fan as the outside air-sending portion 25 and by using an evaporator fan as the inside air-sending portion 26, outside air and inside air are supplied to the permeable membrane 24 with existing devices. In that case, a structure of the ventilating device 1 may be simplified.

Further, according to the present embodiment, the permeable membrane 24 is arranged upstream from the condenser 30 in the outside air introducing passage 32, so that the bypass passage 35 of the fourth embodiment can be omitted.

Sixth Embodiment

A sixth embodiment of the present invention will be described with reference to FIG. 8. In the fifth embodiment, compared with the forth embodiment and the fifth embodiment, a position of a permeable membrane 24 is modified.

The permeable membrane 24 is arranged in a partition 34 separating an outside air introducing passage 32 and an inside air circulation passage 33. The permeable membrane 24 is located downstream from the condenser 30 in the outside introducing passage 32, and is located downstream from the evaporator 31 in the inside air circulating passage 33.

The permeable membrane 24 is arranged on a face of the partition 34 opposing to the evaporator 31, and is located directly under the evaporator 31. The partition 34 has a rib 37 located adjacent to the membrane 24, and the rib 37 prevents water from flowing into the membrane 24.

As shown in FIG. 8, a left side of the partition 34 is slightly lower than a right side of the partition 34. So that, If water is dropped from the evaporator 31 in defrosting operation, the water flows leftward. However, the rib 37 is arranged in the right side of the membrane 24 and prevents the water from flowing into the membrane 24. Therefore, permeability of the membrane 24 may not be deteriorated.

Outside air heated by the condenser 30 flows downward from the condenser 30 in the outside air introducing passage 32. If the outside air heated by the condenser 30 contacts inside air cooled by the evaporator 31 via the membrane 24, heat loss is increased, and cooling efficiency of the ventilating device 1 is lowered. However, in the sixth embodiment, in the same way as the fourth embodiment, a bypass passage 35 is arranged to lead outside air to an outside air passage 22.

Accordingly, outside air not affected by the condenser 30 can be supplied to the permeable membrane 24 located downstream from the condenser 30 in the outside air introducing passage 32. Therefore, temperature difference between outside air of the outside passage 22 and inside air of the inside passage 23 can be reduced, so that the heat loss can be reduced. Thus, loss in the system efficiency can be reduced.

As shown in FIG. 8, outside air flows leftward in the outside air passage 22, and inside air flows leftward in the inside air passage 23. That is, a flow of inside air and outside air are parallel with each other in the parallel state, so that a flow direction of the inside air is same as a flow direction of the outside air via the permeable membrane 24.

According to the present embodiment, by using a condenser fan as the outside air-sending portion 25 and by using an evaporator fan as the inside air-sending portion 26, outside air and inside air are supplied to the permeable membrane 24 with existing devices. In that case, a structure of the ventilating device 1 may be simplified.

Further, the permeable membrane 24 is arranged opposite to the evaporator 31. Thus, the membrane 24 is arranged close to the inside air-sending portion 26, so that inside air blown from the inside air-sending portion 26 can be easily and efficiently supplied to the membrane 24. That is, a drive force of the inside air-sending portion 26 can be used effectively.

Seventh Embodiment

A seventh embodiment of the present invention will be described with reference to FIG. 9. In the seventh embodiment, compared with each of the above-described embodiments, a permeable membrane 24 is arranged in different place.

A permeable membrane 24 is located upstream from the evaporator 31 in the inside air circulating passage 33. The membrane 24 is arranged in a side wall of a housing 10, and an outside air passage 22 is defined out of the housing 10. Thus, air existing outside of the housing 10 is supplied to the membrane 24.

An outside air-sending portion 28 is arranged similarly to the above-described third embodiment shown in FIG. 4. A drive force of an inside air-sending portion 26 is transmitted to the outside air-sending portion 28 by a power transmitter 29, so that an inside air flow and an outside air flow are generated simultaneously in the inside air passage 23 and the outside air passage 22, respectively.

According to the seventh embodiment, by using an evaporator fan as the inside air-sending portion 26, outside air and inside air are supplied to the permeable membrane 24 with existing devices. In that case, a structure of the ventilating device 1 can be simplified.

According to the seventh embodiment, an outside air-sending portion having a motor may be unnecessary. Thus, a configuration of the air-sending portion generating an outside air flow may be simplified.

Further, the outside air passage 22 is exposed to outside of a housing 10, so that outside air contacting the permeable membrane 24 can be easily changed with new air. Therefore, the outside air-sending portion 28 may be omitted.

Other Embodiment

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

The ventilating device 1 is not limited to cool the inside of the housing 10. Alternatively, the temperature in the housing 10 may be controlled to be equal to or higher than a normal temperature.

The ventilation control is not limited to be performed using all of the O₂ sensor 12, the CO₂ sensor 13, and the humidity sensor 14. The ventilation may be controlled using one or two of the sensors 12, 13, 14.

The air-sending portion is not limited to be arranged in each of the outside air passage 22 and the inside air passage 23. Alternatively, the air-sending portion may be arranged in at least one of the air passages 22, 23.

Object stored in the housing 10 is not limited to the green grocery. If the object needs temperature control, and if a concentration of a certain type of gas in the housing 10 is changed when the object is stored in the housing 10, the object may be another food, animal or human.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims. 

1. A ventilating device comprising: a housing, a temperature of inside air of the housing being to be controlled; a gas concentration detector to detect a gas concentration of a predetermined gas in the housing; a passage portion defining an outside air passage through which outside air of the housing flows, and an inside air passage through which inside air of the housing flows; a permeable membrane disposed at an interface defined between the outside air passage and the inside air passage in a manner that a first face of the permeable membrane contacts the outside air flowing through the outside air passage and that a second face of the permeable membrane contacts the inside air flowing thorough the inside air passage, gas permeating the permeable membrane selectively between the outside air passage and the inside air passage; an air sending portion to generate at least one of a flow of the outside air in the outside air passage and a flow of inside air in the inside air passage; and a controller to control the air sending portion, wherein the controller controls at least one of the flow of the inside air and the flow of the outside air by controlling the air sending portion, based on the gas concentration of the predetermined gas detected by the gas concentration detector.
 2. The ventilating device according to claim 1, further comprising: an inside air circulation blower to circulate inside air in the housing, wherein the air sending portion generates the flow of inside air in the inside air passage by introducing a flow of inside air generated by the inside air circulation blower.
 3. The ventilating device according to claim 1, further comprising: a power transmitter, wherein the air sending portion has an inside air sending portion to generate a flow of inside air in the inside air passage, and an outside air sending portion to generate a flow of outside air in the outside air passage, the inside air sending portion has an air-sending fan and a driving portion to drive the fan to rotate, the outside air sending portion is rotated by a rotation force of the driving portion transmitted through the power transmitter.
 4. The ventilating device according to claim 1, wherein the permeable membrane has a pore, and the pore has a diameter equal to or smaller than a mean free path of the predetermined gas.
 5. The ventilating device according to claim 1, further comprising: a condenser in which heat is exchanged between a high temperature refrigerant and outside air; and an evaporator in which heat is exchanged between a low temperature refrigerant and inside air, wherein the air sending portion has an inside air sending portion to generate a flow of inside air in the inside air passage, and an outside air sending portion to generate a flow of outside air in the outside air passage, the outside air sending portion is a fan of the condenser that sends outside air into the condenser, and the inside air sending portion is a fan of the evaporator that sends inside air into the evaporator.
 6. The ventilating device according to claim 5, wherein the permeable membrane is arranged downstream from the evaporator in an air flow and is arranged upstream from the condenser in an air flow.
 7. The ventilating device according to claim 5, further comprising: a bypass passage portion to bypass the condenser so as to supply outside air for the outside air passage, and the permeable membrane is arranged downstream from the evaporator in an air flow and is arranged downstream from the condenser in an air flow. 